Temperature-responsive inductance



June 3, 1930. H. M. WITHEROW TEMPERATURE RESPONSIVE INDUCTANCE OriginalFiled Dec., 13, 1927 Fig 6.

O DEGREES CE NTIGRADE Flg 3 Inventor: Harry M. witherow,

His AUb orr eg.

Patented June 3, 1930 UNITED sures "HARRY M. wIrnEnow, or roar WAYNE,INDIANA, AssIeNon. 'ro GENERAL nLEc'rnIo comm, A CORPORATION or nnw YORKPATENT OFFICE.

rnurnaAirunn-ansronsivn INDUGTANCE Original applicat on filed December13, 192'), Serial No. 239,802. Divided and this application fliedOctober 30, 1928. Serial No. 816,057.

This ap lication is a division of my application erial No. 239,802,filed December 13, 1927, and both applications are assigned to the sameassignee.

My invention relates to temperature compensation of electrical devicesand circuits such as meters, relays, measuring circuits and the like. Ihave found my invention to be useful in connection with awattmeter forcompensating such a meter for that class therein in response to anincrease in temductauce is connected in series with the W of temperatureerrors which are pronounced at low power factors. The invention howeveris not limited to this articular application as will be apparent mm thedescription which follows: Broadly, the invention relates to atemperatureqresponsive inductance device which may be connected in anyelectric circuit to vary the inductance of such circuit in response totemperature changes. To obtain this result I provide an.

inductance device having a core; or magnetic circuit made from amaterial the permeability of which varies with temperature changes. 2

I The features of my invention which are believed to be novel andpatentable will be pointed out in the claims-appended hereto.- For abetter understandin o perature; Fig. 3 shows how the opposite effect maybe accomplished b the temperature responsive in uctance as a shunt; Fig.i illustrates the use of my invention ina transformer in which the coreis made of a material having a negative temperature coecient ofpermeability; Fig. 5 represents the use of the invention forcompensatina wattmeterfor temperature er rors in wch my temperatureresponsive inlag 6 and l are coil of the meter; and Figs.

employing vector diagrams explanatory of the potential percentages beingabout 68% nickel, 30% a copper and 2% iron. Such an alloy when cast andthen quenched in water as soon as itsolidifies will give a negativetemperature coeiiicicnt of permeabilit the character represente inFig. 1. This alloy is not my invention but rather the invention of IsaacF. Kinnard, and is more fully described and claimed in his Patent No.1,706,172, March 19, 1929. I do not confine my invention to the use ofthis particular material but mention it as one which I have found togive beneficial results in the application of my invention representedin A simple application of the invention is represented in Fig. 2.. Inthis figure I have represented a voltage responsive rela for use onalternating current circuits. f the relay coil 10 is made of copper, orsome other material having a positive temperature coefficient ,ofresistance, its resistance will increase with an increase intemperatureand ordinarily its current will decrease for the same operating voltage.The relay will thus have a temperature .-error. for such error I connectmy tem erature responsive inductance device in series with the relaycoil. This device merely consists of a coil 11 wound on a closed core 12made of a material having a ne ative temperature coeflicient ofpermeability and placed so that it is subject to the same temperature asthe relay coil 10. If this core 12 has thelcharactcristics representedin Fig. 1, it will have an appreciable inductance at zero degreescentigrade for exampleand its inductance will gradually decrease as thetemperature increases until at about 100 degrees ceuti substantially ofTo compensate the operation of the relay will thus be independent oftemperature changes. It is of course assumed that the frequency of thesupply voltage remains substantially constant.

In Fig. 3, 13 represents an A. C. voltmeter which requires a resistance14 in its circuit. If the meter and resistance have a combined positivetemperature coefficient of resistance the meter circuit will be subjectto a temperature error. To compensate for this I connect my inductance11, 12 in shunt to a suitable value of resistance 14 so.

as to maintain the current through the meter 13 independent oftemperature changes.

Fig. 4 represents the use of my inductance device as a temperaturecompensating transformer. In this case 13 may represent an A. C.voltmeter, as in Fig. 3, which has a positive temperature coeflicient ofresistance. 14 represents a transformer core made of a material thepermeability of which decreases with an increase in temperature. 15represents the primary coil connected across the voltage source measuredby meter 13, and 16 represents the secondary coil connected in thevoltmeter circuit. In this case the transformer connection is such thatthe transformer bucks the voltage in the voltmeter circuit. At lowtemperatures'there will be an appreciable transformer action which willgradually decrease as the temperature increases. By using thepropernumber of turns on the primary and secondary windings the decreasein transformer action may be adjusted to just compensate for theincreasein resistance in the meter circuit as the temperature increases. Theprimary winding of the transformer will preferably be of high resistanceso that its current will not become excessive as the transformer actiondecreases.

In the applications above explained the temperature responsiveinductance has been employed to simply vary the current [in analternating current circuit in response to temperature changes. Itbeinga variable inductance it of course varies the phase angle of thecurrent in the circuit and in Fig. 5 I have made use of this variablecharacteristic as well as the variable current characteristic incompensating a wattmeter for temperature errors which tend to cause aperature.

shift in the phase angle between the voltage and current fluxes. v

It is well known that in the induction wattmeter the phase angle betweenthe cur rent and voltage fluxes should be in a 90 degree relation atunity power factor. The greater part of this 90 degree relation isproduced by the voltage coil because of its high inductance and theremainder is usually produced by a lag coil which is placed in inductiverelation with the potential flux. In Fig. 5, 17 represents the currentcore, 18

the current coil, 19 the voltage core, 20 the voltage coil, 21 therotatably mounted induction disc, 22 the drag magnet and 23 the lag coilof an induction watthour meter.

Ordinarily the lag coil comprises a closed coil of one or more turnsplaced near the tip of the potential coil and adjustment is i vector IR.As a result the vector of the voltage coil flux represented by I E issomewhat less than 90 degrees from the line voltage vector V. To makethe angle between V and DE 90 degrees a lag coil is employed and thevoltage induced in it by transformer action may be represented by thevector EL. The lag coil is largely resistance and its flux vector may berepresented by PL. The resultant of I E and PL is represented by I Rwhich establishes the desired 90 degree relation between the linevoltage and the potential flux of the meter at some given tem- Thevoltage and lag coils are usually made of copper which has a positivetemperature coefficient of resistance. Consequently at some highertemperature the resistance drop in the voltage coil increases and thevector-IR increases causing the vector I Eto shift to I E'. Theresistance of the lag coil also increases and its current thereforedecreases so that its flux vector becomes smaller but does not change indirection to any noticeable extent and may be represented by I L. Thenew resultant potential flux of the meter is represented at @R which isappreciably less than 90 degrees from the line voltage vector V. Thisexplains the cause of the phase angle temperature error of this type ofmeter. This temperature error does not materially affect the accuracy ofthe motor near unity power factors but at low ower factors where aslight shift in the p ase angle between current and voltage fluxes ismore serious this type of temperature error produces an appreciableerror in meter accuracy. The vector of the current flux has not beenshown but it will be understood that its vector direction is dependentsolely upon the power factor and is in phase with the vector V at unitypower factor.

To compensate for this class of temperature errors in meters of theinduction t pe I connect my temperature responsive in netance in serieswith the lag coil as represented in Fig. 5. Forthe purpose ofconvenience in assembling, the core 12 of the temperature responsiveinductance is split in two parts and fastened together by a brass bolt24 after the coil 1.1 is slipped on the central leg. For a cycle meterof standard design I have found that a lag coil 23 having six turns ofcopper connected in series with about 25 turns in the coil 11 willproduce the temperature compensation depicted in Fig. 7 where the samedesignation is used as in Fig. 6. The vectors V, E, IR and I E remainunchan ed. The vector I L due to the inductance 1n the circuit of thelag coil has an increased angle with the vector EL at some lowtemperature such as 0 centigrade. The resultant of I L and @E or I R iscorrectly displaced at degrees from V. Now as the temperature increasesthe inductance in the circuit" of the lag coil decreases. The current inthe lag coil circuit increases and becomes more nearly in phase with itsinduced voltage as repre-. sented at I L'. The potential flux of themeter at the higher temperature is the resultant of I E' and @L or @Rand is the same both in direction and in ma nitude as it was at the lowtemperature. T us use is made of both the change in current and thechange in phase angle produced by the temperature responsive inductanceto compensate the meter for this class of temperasaid core member forproducing a flux therein, said core member having an appreciablepelgative temperature coeflicient of permeaiit 3. A temperatureresponsive reactance comprising a core member, a winding for producing aflux in said core member, the core member being made of a material whichis substantially non-magnetic at about degrees centigrade and which hasa substantially linear negative temperature coeflicient of permeabilitybelow such temperature.

4. Temperature responsive reactance comprising a core member providedwith an energizing winding, said core member comprising an alloycomposed of approximately 68% nickel and 30% copper and 2% iron, andhaving a substantially linear negative temperature coefficient ofpermeability over a temperature range of at least 40 degrees centigradeand including zero degrees centigrade.

In witness whereof I have hereunto set my hand this 27th day of October,1928.

HARRY M. VVITHEROW.

ture errors over the usual range of temperature changes met with inpractice.

In accordance with the provisions of the patent statutes I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof;but I desire to have it understood that the apparatus. shown anddescribed is only illustrative and that the invention may be carried outby other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A temperature responsive reactance having a core member made of amaterial which is magnetic at zero degrees centigrade and which issubstantially non-magnetic at. i

100 degrees centigrade and an energizing winding on said core member.

2. temperature responsive reactance comprismg a core member, a wmdmg on

